Asymmetric conformations and lipid interactions shape the ATP-coupled cycle of a heterodimeric ABC transporter.

Here we used cryo-electron microscopy (cryo-EM), double electron-electron resonance spectroscopy (DEER), and molecular dynamics (MD) simulations, to capture and characterize ATP- and substrate-bound inward-facing (IF) and occluded (OC) conformational states of the heterodimeric ATP binding cassette (ABC) multidrug exporter BmrCD in lipid nanodiscs. Supported by DEER analysis, the structures reveal that ATP-powered isomerization entails changes in the relative symmetry of the BmrC and BmrD subunits that propagates from the transmembrane domain to the nucleotide binding domain. The structures uncover asymmetric substrate and Mg2+ binding which we hypothesize are required for triggering ATP hydrolysis preferentially in one of the nucleotide-binding sites. MD simulations demonstrate that multiple lipid molecules differentially bind the IF versus the OC conformation thus establishing that lipid interactions modulate BmrCD energy landscape. Our findings are framed in a model that highlights the role of asymmetric conformations in the ATP-coupled transport with general implications to the mechanism of ABC transporters.

Asymmetric conformations and lipid interactions shape the ATP-coupled cycle of a heterodimeric ABC transporter.

To illuminate the structural origin of catalytic asymmetry of heterodimeric ABC transporters and how it shapes the energetics of their conformational cycles, we used cryo-electron microscopy (cryo-EM), double electron-electron resonance spectroscopy (DEER), and molecular dynamics (MD) simulations, to capture and characterize conformational states of the heterodimeric ABC multidrug exporter BmrCD in lipid nanodiscs. In addition to multiple ATP- and substrate-bound inward-facing (IF) conformations, we obtained the structure of an occluded (OC) conformation wherein the unique extracellular domain (ECD) twists to partially open the extracellular gate. In conjunction with DEER analysis of the populations of these conformations, the structures reveal that ATP-powered isomerization entails changes in the relative symmetry of the BmrC and BmrD subunits that propagates from the transmembrane domain (TMD) to the nucleotide binding domain (NBD). The structures uncover asymmetric substrate and Mg 2+ binding which we hypothesize are required for triggering ATP hydrolysis preferentially in one of the nucleotide-binding sites. MD simulations demonstrated that multiple lipid molecules, identified from the cryo-EM density maps, differentially bind the IF versus the OC conformation thus modulating their relative stability. In addition to establishing how lipid interactions with BmrCD modulate the energy landscape, our findings are framed in a distinct transport model that highlights the role of asymmetric conformations in the ATP-coupled cycle with implications to the mechanism of ABC transporters in general.

The epidemic of acute lymphoid leukemia in China: current trends and future prediction.

Background: China has experienced one of the fastest increases in the incidence of acute lymphoid leukemia (ALL). The aim of this study was to assess the long-term trends of the incidence and mortality of ALL in mainland China between 1990 and 2019 and to project these trends through 2028. Methods: Data on ALL were extracted from the Global Burden of Disease Study 2019; population data were extracted from World Population Prospects 2019. An age-period-cohort framework was used in the analysis. Results: The net drift for the incidence of ALL was 7.5% (95% confidence interval [CI]: 7.1%, 7.8%) per year in women and 7.1% (95% CI: 6.7%, 7.6%) in men, and local drift was found to be higher than 0 in every studied age group (p<0.05). The net drift for mortality was 1.2% (95% CI: 1.0%, 1.5%) in women and 2.0% (95% CI: 1.7%, 2.3%) in men. Local drift was lower than 0 in boys aged 0-4 years and girls aged 0-9 years and higher than 0 in men aged 10-84 years and women aged 15-84 years. The estimated period relative risks (RRs) for both incidence and mortality showed increasing trends in the recent period. The cohort RRs for incidence showed increasing trends in both sexes; however, the cohort RR for mortality was decreased in the recent birth cohort (women born after 1988-1992 and men born after 2003-2007). Compared with that in 2019, the incidence of ALL in 2028 is projected to increase by 64.1% in men and 75.0% in women, and the mortality is predicted to decrease by 11.1% in men and 14.3% in women. The proportion of older adult/adults individuals with incident ALL and ALL-related death was projected to increase. Conclusions: Over the last three decades, the incidence and mortality rates of ALL have generally increased. It is projected that the incidence rate of ALL in mainland China will continue to increase in the future, but the associated mortality rate will decline. The proportion of older adult/adults individuals with incident ALL and ALL-related death was projected to increase gradually among both sexes. More efforts are needed, especially for older adult/adults individuals.

Oily cold rolling mill sludge conditioned by quicklime to improve dewatering performance: optimization and mechanism study.

Dewatering is critical to oily cold rolling mill (CRM) sludge treatment. Therefore, finding an efficient, energy-saving, and applicable dewatering technology for oily CRM sludge is still urgent. This study investigated the performance of quicklime as a conditioning agent for oily CRM sludge conditioning and dewatering. The interactive effects of quicklime dosage, temperature, and time on filter cake's specific resistance to filtration (SRF) and the dewatering rate of oily CRM sludge were studied by response surface methodology (RSM). The optimal parameters for conditioning oily CRM sludge were quicklime dosage of 18.7%, temperature of 54 °C, and time of 43.3 min, which resulted in filter cake SRF of 0.50 × 1010 m/kg and dewatering rate of 61.2%. The viscosity of oily CRM sludge could be reduced by 90% after conditioned with quicklime, which caused by the neutralization or hydrolysis of high viscosity organic matter in the oil phase with quicklime to produce low viscosity organic matter. The study indicated the excellent performance of quicklime as a conditioning agent for oily CRM sludge treatment and provided an effective route for the recycling of the oily CRM sludge for steel production.

Hybrid biointerface engineering nanoplatform for dual-targeted tumor hypoxia relief and enhanced photodynamic therapy.

The clinical application of photodynamic therapy (PDT) is limited by the lack of tumor selectivity of photosensitizer (PS) and the hypoxic tumor microenvironment (TME). To address these limitations of PDT, we developed a hybrid engineered biointerface nanoplatform that integrated anti-epidermal growth factor receptor (EGFR)-aptamer (EApt)-modified liposomes with tumor cell membranes (TMs) to create M/L-EApt. M/L-EApt exhibited enhanced stability and significant dual-targeting ability, enabling selectively accumulate in hypoxic tumor regions after systemic infusion. PHI@M/L-EApt, formed by M/L-EApt loaded with an oxygen carrier perfluorotributylamine (PFTBA) and IR780 (a PS), effectively promoted the therapeutic performance of PDT by reversing the hypoxic TME and increasing the accumulation of IR780 at the tumor sites, resulting in a robust anti-tumor efficacy. In vivo results showed that PHI@M/L-EApt treatment effectively suppressed the growth of triple-negative breast tumors in mice. Our findings demonstrated the synergistic effect of oxygen supply and PDT on tumor treatment using PHI@M/L-EApt. This study presented a biomimetic interface engineering strategy and dual-targeted hybrid nanoplatform for relieving hypoxic TME and potentially facilitating the clinical application of PDT.

Recent Advances in Alkali-Activated Materials with Seawater and Sea Sand.

The development of sustainable cementitious materials is essential and urgent for the construction industry. Benefiting from excellent engineering properties and a reduced greenhouse gas footprint, alkali-activated materials (AAM) are among the robust alternatives to Portland cement for civil infrastructure. Meanwhile, concrete production also accounts for around 20% of all industrial water consumption, and the global freshwater shortage is increasing. This review discusses recent investigations on seawater-mixed AAMs, including the effects of seawater on workability, reaction mechanism, shrinkage, short and long-term strength, binding of chloride and corrosion of steel reinforcement. Attention is also paid to the utilization of sea sand as aggregate, as well as discussions on the challenges and further research perspectives on the field application of AAMs with seawater and sea sand.

Co-treatment of municipal solid waste incineration fly ash (MSWI FA) and municipal sludge: A innovative method to improve sludge dewatering with fly ash dechlorination.

The complexity of municipal sludge dewatering is a bottleneck problem limiting resource utilization. In this paper, adding municipal solid waste incineration fly ash (MSWI FA) to municipal sludge for enhanced dewatering was applied, while the chlorine salt in MSWI FA was simultaneously removed using water in municipal sludge. The effects of different dosages and chemical components of MSWI FA on municipal sludge dewatering, and the removal effect of municipal sludge washing on Cl element were investigated. The results showed that the municipal sludge's specific resistance to filtration after co-treatment was significantly reduced, and more hydrophobic channels were formed in the vacuum suction filtration of the treated municipal sludge, conducive to efficient water removal. The moisture content of municipal sludge was reduced from 96.0% to 48.3%, and the moisture reduction rate increased from 17.7% to 32.1%. The chemical composition of MSWI FA could effectively promote the dewatering of municipal sludge, among which CaO was the best, followed by CaCl2 and NaCl, and KCl was the worst. Simultaneously, the municipal sludge showed a good effect on removing Cl from MSWI FA. The minimum Cl content in the mixture after Co-treatment is 1.5%. These results could provide a new way to dispose of MSWI FA and municipal sludge.

Basic Research on Co-treatment of Municipal Solid Waste Incineration Fly Ash and Municipal Sludge for Energy-Saving Melting.

MSWI fly ash and municipal sludge are solid wastes. Melting vitrification treatment was a resource utilization method. However, the flow temperature of grate furnace MSWI fly ash and municipal sludge was high (>1325 °C), which increased the energy consumption in the melting process. MSWI fly ash contained a large amount of CaO, and municipal sludge contained a large amount of SiO2, Al2O3, and Fe2O3. The temperature of melting vitrification can be reduced using these two kinds of CITY garbage as raw materials to change the proportion of ingredients. The eutectic characteristics of MSWI fly ash and municipal sludge and the phase diagrams of CaO-SiO2-Al2O3 (C-S-A) and CaO-SiO2-Al2O3-Fe2O3 (C-S-A-F) were analyzed in this paper. It established a low melting point mixing system. The results showed that when the amount of municipal sludge was 50-70%, the flow temperature of the mixtures was <1215 °C, which was significantly lower than that of MSWI fly ash (1490 °C) and municipal sludge (1325 °C). The optimal range of low melting point components was 14.1-36.3% CaO, 21.6-40.4% SiO2, 6.7-12.6% Al2O3, and 6.3-11.4% Fe2O3. At 400-1400 °C, the minerals in the mixtures mainly changed as follows: CaCO3 + SiO2 + Al2O3 → Ca2SiO4 + Ca3SiO5 + Ca2Al2SiO7 + Ca3Al2O6 + Ca12Al14O33 → CaAl2Si2O8. In the melting experiment, with the increase in temperature, most of the phases in the mixtures might become amorphous. Therefore, the low melting point phase anorthite (CaAl2Si2O8) only accounted for a small part of the final molten product.

Enhancing the Dewaterability of Oily Cold Rolling Mill Sludge Using Quicklime as a Conditioning Agent.

The high moisture and viscosity characteristics of oily cold rolling mill (CRM) sludge led to limitations in its recycling. In this paper, the results of using quicklime as a conditioning agent to improve the dewaterability of the oily CRM sludge cake were reported. Quicklime was selected as the best conditioning agent through conditioning-dewatering experiments because it could effectively reduce the viscosity of oily CRM sludge and improve the dewaterability of the oil sludge filter cake. The optimal conditioning effect was obtained when the quicklime dosage was 10%, the temperature was 60 °C, the liquid/solid ratio was 1.5:1, and the time was 30 min. The reduction of specific resistance to filtration was 95.9%, and the coefficient of compressibility of the filter cake decreased from 1.11 to 0.89. The dewatering rate increased from 9.0 to 52.6%. The oily CRM sludge cake formed an incompressible rigid porous structure because of conditioning with quicklime. In addition, after conditioning with quicklime, the oil content, chemical oxygen demand, and turbidity of the filtrate decreased, and the composition of the dried filter cake met the requirements of ironmaking raw materials. Using quicklime to condition the oily CRM sludge provided a green approach to waste recovery and sustainable management.

Asymmetric drug binding in an ATP-loaded inward-facing state of an ABC transporter.

Substrate efflux by ATP-binding cassette (ABC) transporters, which play a major role in multidrug resistance, entails the ATP-powered interconversion between transporter intermediates. Despite recent progress in structure elucidation, a number of intermediates have yet to be visualized and mechanistically interpreted. Here, we combine cryogenic-electron microscopy (cryo-EM), double electron-electron resonance spectroscopy and molecular dynamics simulations to profile a previously unobserved intermediate of BmrCD, a heterodimeric multidrug ABC exporter from Bacillus subtilis. In our cryo-EM structure, ATP-bound BmrCD adopts an inward-facing architecture featuring two molecules of the substrate Hoechst-33342 in a striking asymmetric head-to-tail arrangement. Deletion of the extracellular domain capping the substrate-binding chamber or mutation of Hoechst-coordinating residues abrogates cooperative stimulation of ATP hydrolysis. Together, our findings support a mechanistic role for symmetry mismatch between the nucleotide binding and the transmembrane domains in the conformational cycle of ABC transporters and is of notable importance for rational design of molecules for targeted ABC transporter inhibition.

Structure, dynamics, and regulation of TRF1-TIN2-mediated trans- and cis-interactions on telomeric DNA.

TIN2 is a core component of the shelterin complex linking double-stranded telomeric DNA-binding proteins (TRF1 and TRF2) and single-strand overhang-binding proteins (TPP1-POT1). In vivo, the large majority of TRF1 and TRF2 exist in complexes containing TIN2 but lacking TPP1/POT1; however, the role of TRF1-TIN2 interactions in mediating interactions with telomeric DNA is unclear. Here, we investigated DNA molecular structures promoted by TRF1-TIN2 interaction using atomic force microscopy (AFM), total internal reflection fluorescence microscopy (TIRFM), and the DNA tightrope assay. We demonstrate that the short (TIN2S) and long (TIN2L) isoforms of TIN2 facilitate TRF1-mediated DNA compaction (cis-interactions) and DNA-DNA bridging (trans-interactions) in a telomeric sequence- and length-dependent manner. On the short telomeric DNA substrate (six TTAGGG repeats), the majority of TRF1-mediated telomeric DNA-DNA bridging events are transient with a lifetime of ~1.95 s. On longer DNA substrates (270 TTAGGG repeats), TIN2 forms multiprotein complexes with TRF1 and stabilizes TRF1-mediated DNA-DNA bridging events that last on the order of minutes. Preincubation of TRF1 with its regulator protein Tankyrase 1 and the cofactor NAD+ significantly reduced TRF1-TIN2 mediated DNA-DNA bridging, whereas TIN2 protected the disassembly of TRF1-TIN2 mediated DNA-DNA bridging upon Tankyrase 1 addition. Furthermore, we showed that TPP1 inhibits TRF1-TIN2L-mediated DNA-DNA bridging. Our study, together with previous findings, supports a molecular model in which protein assemblies at telomeres are heterogeneous with distinct subcomplexes and full shelterin complexes playing distinct roles in telomere protection and elongation.

Self-Compacting Alkali-Activated Materials: Progress and Perspectives.

Alkali-activated materials (AAMs) are considered to be alternative cementitious materials for civil infrastructures. Nowadays, efforts have been made in developing AAMs with self-compacting ability. The obtained self-compacting AAMs (SCAAMs) accomplish superior passing and filling properties as well as excellent mechanical and environmental advantages. This work critically revisits recent progresses in SCAAMs including mixture proportions, fresh properties, mechanical strength, microstructure, acid and sulfate resistance, high temperature behaviors, impact resistance and interface shear strength. To facilitate direct comparison and interpretation of data from different publications, mixture proportions were normalized in terms of the content of key reactive components from precursors and activators, and correlation with mechanical behaviors was made. Moreover, special attention was paid to current research challenges and perspectives to promote further investigation and field application of SCAAMs as advanced construction material.

Influences of fine-grained NaCl particles on performance and denitration efficiency of activated carbon during sintering flue gas purification process.

Alkali metal chlorides emitted from sintering flue gas are easily adsorbed on the surface of activated carbon (AC) in the purification process. In this paper, NaCl particles adsorbing onto AC were simulated by impregnation method, and the size and morphology of NaCl particles were similar to those of NaCl-PM10 emitted from sintering flue gas. With the adsorption of NaCl particles, 2-10-µm pores of AC were filled, and the specific surface area of AC decreased. But NaCl led to the increase of acidic functional groups on the surface of AC. When 0.75 wt% NaCl was adsorbed, it was beneficial for AC catalytic denitration (de-NOx), because the chemical reaction was strengthened by acidic functional groups, so it showed a certain promotion of de-NOx efficiency. As 1.5 wt% NaCl and 3 wt% NaCl were adsorbed, NaCl had an inhibitory effect on AC de-NOx, which was because the specific surface area of AC decreased, and the prevention of physical adsorption played a major role. As a result, the de-NOx efficiency of AC adsorbed with 3 wt% NaCl decreased from 40.59 to 23.02% at 150 °C. Therefore, the absorption of NaCl fine particles on AC should not exceed 0.75 wt%.

Mechanism of vaccinia viral protein B14-mediated inhibition of IκB kinase ß activation.

Activation of IκB kinase ß (IKKß) is a central event in the NF-κB-mediated canonical pro-inflammatory pathway. Numerous studies have reported that oligomerization-mediated trans autophosphorylation of IKKß is indispensable for its phosphorylation, leading to its activation and IKKß-mediated phosphorylation of substrates such as IκB proteins. Moreover, IKKß's interaction with the NF-κB essential modifier (NEMO) is necessary for IKKß activation. Interestingly, some viruses encode virulence factors that target IKKß to inhibit NF-κB-mediated antiviral immune responses. One of these factors is the vaccinia viral protein B14, which directly interacts with and inhibits IKKß. Here we mapped the interaction interface on the B14 and IKKß proteins. We observed that B14 binds to the junction of the kinase domain (KD) and scaffold and dimerization domain (SDD) of IKKß. Molecular docking analyses identified key interface residues in both IKKß and B14 that were further confirmed by mutational studies to promote binding of the two proteins. During trans autophosphorylation of protein kinases in the IKK complex, the activation segments of neighboring kinases need to transiently interact with each other's active sites, and we found that the B14-IKKß interaction sterically hinders direct contact between the kinase domains of IKKß in the IKK complex, containing IKKß, IKKα, and NEMO in human cells. We conclude that binding of B14 to IKKß prevents IKKß trans autophosphorylation and activation, thereby inhibiting NF-κB signaling. Our study provides critical structural and mechanistic information for the design of potential therapeutic agents to target IKKß activation for the management of inflammatory disorders.

The Extracellular Domain of Pollen Receptor Kinase 3 is structurally similar to the SERK family of co-receptors.

During reproduction in flowering plants, the male gametophyte delivers an immotile male gamete to the female gametophyte in the pistil by formation of pollen tubes. In Arabidopsis thaliana, two synergid cells situated on either side of the egg cell produce cysteine-rich chemoattractant peptide LURE that guides the pollen tube to the female gametophyte for sexual reproduction. Recently, in Arabidopsis thaliana, Pollen Receptor Kinase 3 (PRK3), along with PRK1, PRK6, and PRK8, have been predicted to be the receptors responsible for sensing LURE. These receptors belong to the Leucine Rich Repeat Receptor Like Kinases (LRR-RLKs), the largest family of receptor kinases found in Arabidopsis thaliana. How PRKs regulate the growth and development of the pollen tube remains elusive. In order to better understand the PRK-mediated signaling mechanism in pollen tube growth and guidance, we have determined the crystal structure of the extracellular domain (ecd) of PRK3 at 2.5 Å, which resembles the SERK family of plant co-receptors. The structure of ecdPRK3 is composed of a conserved surface that coincides with the conserved receptor-binding surface of the SERK family of co-receptors. Our structural analyses of PRK3 have provided a template for future functional studies of the PRK family of LRR-RLK receptors in the regulation of pollen tube development.

Characterization of neurovascular compression in facial neuralgia patients by 3D high-resolution MRI and image fusion technique.

OBJECTIVE: To describe the anatomical characteristics and patterns of neurovascular compression (NVC) in patients suffering trigeminal neuralgia (TN) by 3D high-resolution magnetic resonance imaging (MRI) method and image fusion technique. METHODS: The anatomic structure of trigeminal nerve, brain stem and blood vessel was observed in 100 consecutive TN patients by 3D high resolution MRI (3D SPGR, contrast-enhanced T1 3D MP-RAGE and T2/T1 3D FIESTA). The 3D image sources were fused and visualized using 3D DOCTOR software. RESULTS: One or several NVC sites, which usually appeared 0-9.8 mm away from brain stem, were found on the symptomatic side in 93% of the TN cases. Superior cerebellar artery was involved in 76% (71/93) of these cases. The other vessels including antero-inferior cerebellar artery, vertebral artery, basilar artery and veins also contributed to the occurrence of NVC. The NVC sites were found to be located in the proximal segment in 42% of these cases (39/93) and in the distal segment in 45% (42/93). Nerve dislocation or distortion was observed in 32% (30/93). CONCLUSIONS: Various 3D high resolution MRI methods combined with the image fusion technique could provide pathologic anatomic information for the diagnosis and treatment of TN.

Tet-mediated formation of 5-carboxylcytosine and its excision by TDG in mammalian DNA.

The prevalent DNA modification in higher organisms is the methylation of cytosine to 5-methylcytosine (5mC), which is partially converted to 5-hydroxymethylcytosine (5hmC) by the Tet (ten eleven translocation) family of dioxygenases. Despite their importance in epigenetic regulation, it is unclear how these cytosine modifications are reversed. Here, we demonstrate that 5mC and 5hmC in DNA are oxidized to 5-carboxylcytosine (5caC) by Tet dioxygenases in vitro and in cultured cells. 5caC is specifically recognized and excised by thymine-DNA glycosylase (TDG). Depletion of TDG in mouse embyronic stem cells leads to accumulation of 5caC to a readily detectable level. These data suggest that oxidation of 5mC by Tet proteins followed by TDG-mediated base excision of 5caC constitutes a pathway for active DNA demethylation.